The correct answer is: None of the above.
Amazon Simple Queue Service (SQS) is a fully managed message queuing service that enables you to decouple and scale microservices, distributed systems, and serverless applications. SQS can be used to send, store, and receive messages between applications running on different servers.
Amazon Elastic Compute Cloud (EC2) is a cloud computing service that provides resizable compute capacity in the cloud. EC2 instances are virtual servers that you can use to run your applications. You can choose from a variety of instance types, operating systems, and software bundles to create the right environment for your needs.
Amazon Simple Notification Service (SNS) is a fully managed pub/sub messaging service that enables you to decouple microservices, distributed systems, and serverless applications. SNS can be used to send messages to a large number of subscribers, including mobile devices, email addresses, and HTTP/S endpoints.
None of these services is the central application in the AWS portfolio. The central application in the AWS portfolio is Amazon Web Services (AWS), which is a cloud computing platform that provides infrastructure and services to businesses and individuals. AWS offers a broad set of global compute, storage, database, analytics, application, and deployment services that help organizations move faster, lower IT costs, and scale applications.